In recent years, apparatuses which conform to a method such as Moving Picture Experts Group (MPEG) have been widely spread for both of information delivery in broadcasting stations or the like and information reception in ordinary homes. MPEG compresses the image information through orthogonal transform such as discrete cosine transform and motion compensation by using redundancy unique to the image information.
Particularly, an MPEG2 (ISO/IEC 13818-2) method is defined as a general use image coding method, and is currently widely used in extensive applications for professional use and consumer use as a standard covering both an interlaced scanning image and a progressive scanning image, and a standard resolution image and a high definition image. By the use of the MPEG2 method, it is possible to realize a high compression ratio and good image quality, for example, by assigning a bit rate of 4 Mbps to 8 Mbps to an interlaced scanning image of a standard resolution having 720×480 pixels and assigning a bit rate of 18 Mbps to 22 Mbps to an interlaced scanning image of a high resolution having 1920×1088 pixels.
MPEG2 has mainly targeted high image quality coding suitable for broadcasting, but has not handled a coding method at a bit rate lower than that in MPEG1, that is, at a higher compression ratio. With the wide use of portable terminals, the desire for such a coding method has been considered to increase, and thus an MPEG4 coding method has been standardized so as to correspond thereto. In relation to an image coding method of MPEG4, a standard thereof was approved as an international standard entitled ISO/IEC 14496-2 in December 1998.
In addition, in recent years, standardization of a standard called H.26L (ITU-T Q6/16 VCEG) has progressed for the original purpose of image coding for video conference use. H.26L uses a larger calculation amount due to coding and decoding than the coding method of the related art such as MPEG2 or MPEG4, but is known for realizing higher coding efficiency.
Further, as part of activities of MPEG4, Joint Model of Enhanced-Compression Video Coding is currently being standardized in order to realize higher coding efficiency by also incorporating functions which are not supported by H.26L, on the basis of H.26L. As for the standardization schedule thereof, the coding method has become an international standard under the name of H.26L and MPEG-4 Part 10 ((Advanced Video Coding (AVC)) in March 2003.
In addition, as an extension of the AVC method, Fidelity Range Extension (FRExt) which includes coding tools for use in business such as RGB or YUS422 and YUV444 and also includes 8×8 DCT or quantization matrix defined in MPEG2 was standardized in February 2005. This realizes a coding method in which even film noise included in a movie can be favorably expressed by using the AVC method, and thus leads to use for various applications such as a Blu-Ray (registered trademark) disc (BD).
However, recently, there have been increasing demands for higher compression ratio coding, such as a demand for compression of an image with about 4000×2000 pixels which is four times the size of a high-vision image or a demand for delivery of a high-vision image in limited transmission capacity circumstances such as the Internet. For this reason, study of improvement of coding efficiency is being currently performed in Video Coding Expert Group (VCEG) affiliated to the above ITU-T.
In addition, currently, for the purpose of improvement in higher coding efficiency than that of AVC, standardization of a coding method called High Efficiency Video Coding (HEVC) is in progress by Joint Collaboration Team-Video Coding (JCTVC) which is a joint standardization organization of ITU-T and ISO/IEC. NPL 1 has been currently published as a draft in August 2013.
Meanwhile, recently, with the progress of techniques, a high dynamic range (HDR) display with the maximum luminance of 500 nit or 1000 nit has been started to be sold on the market.
In a case where a standard dynamic range (SDR) display and an HDR display are mixed, it is necessary to encode each of an SDR image and an HDR image in the AVC method or the HEVC method, and thus a data amount increases. Therefore, a method is considered in which one of the SDR image and the HDR image is coded, and then a dynamic range is converted after decoding is performed as necessary, thereby generating the other.